Intraocular lenses (IOLs) are routinely implanted in patients' eyes during cataract surgery to replace the natural crystalline lens. IOLs may include monofocal IOLs providing a single focus point (e.g., distance vision) and multifocal IOLs providing two or more focus points (e.g., trifocal IOLs providing distance vision, intermediate vision, and near vision). Multifocal IOLs may include diffractive surface profiles, which may include a number of concentric, ring-shaped echelettes that diffract light into several directions simultaneously. Such diffractive surface profiles may provide multiple diffraction orders and focus the light into various images corresponding to different focal lengths of the lens.
Due to the dispersion properties of the lens and the eye, all IOLs (including multifocal IOLs) may exhibit chromatic aberrations where blue light focus in front of the retina and red light focus behind the retina. Such out-of-focus light degrades the lens' overall efficiency in concentrating broadband light energy onto the patient's retina and may impede patients' functional vision (such as low contrast visual acuity under photopic and mesopic conditions at distance). This problem may be particularly bothersome for patients having multifocal IOLs where light is divided among multiple focus points.
Accordingly, there is a need for a multifocal IOL having an optical design that provides chromatic aberration correction.